To produce ethanol from grass, fuel farmers need land on which to grow the grass. But with over 7 billion hungry mouths on this planet, high quality farmland is needed more urgently to fill bellies than gas tanks.

Luckily for the would-be fuel farmer, many grasses can thrive in areas where corn or rice would wither and die. Recent research suggests there may be enough of that land to provide over 50 percent of our current liquid fuel needs.

Researchers at the University of Illinois analyzed land-use maps to determine just how much land was suitable for growing biofuel crops without encroaching on agricultural lands. Lead researcher, Ximing Cai, and his team looked first at marginal lands, like abandoned and degraded farmland.

An estimated 790 million acres of worn-out cropland are now lying unused and could be converted to biofuel crops without putting more land under the plow or encroaching on existing farms, they report.

Further estimates looked at the amount of land available if natural grasslands, such as savannas and prairies, were managed for fuel production. The possible biofuel farmland increases to 3,486 million acres if both natural grasslands and mixed-use pasture lands are considered.

Though less productive than monocultures of specific species like switchgrass and miscanthus, native grasslands require very little investment and maintenance. The system is referred to as Low Investment/High Diversity. Mixed species native grasslands, managed for fuel production, also shelter higher numbers of bird species than either corn or switchgrass fields, according to other recent research.

Much of the potential biofuel cropland is in the developing world, with as much as one-third in Africa. This could provide for local fuel needs and improve regional economies. But the researchers note that exporting fuel from developing area to places with higher demand would require additional energy and infrastructure, reducing efficiency of production and changing the economic feasibility.

While it sounds like the research suggests biofuel cropland is plentiful, the researchers pointed out that real world complexities can make potential areas impossible. The real deciding factors will be global energy and food markets, they said. By making an estimate of available land, the researchers hope to lay the foundation for further research into the feasibility of growing grasses for the production of ethanol.

“We hope this will provide a physical basis for future research,” Cai said in a press release. “For example, agricultural economists could use the dataset to do some research with the impact of institutions, community acceptance and so on, or some impact on the market. We want to provide a start so others can use our research data.”

To make their estimates, Cai's team compiled data about soil quality, land use, climate and topography from maps and other records. A computer simulation then used fuzzy logic to analyze that data and estimate potential ethanol production.

Fuzzy logic is a mathematical technique that allows estimations from approximated data and deals with uncertainty. It was necessary in this research because land productivity is dependent on many factors that can not be known before the actual growing season.